The present invention is in the field of non-mechanical printer or copying devices and is particularly concerned with a discharge device for efficiently and rapidly removing a developer mix from a developing station.
2. Description of the Prior Art
In copying device technology, and in non-mechanical fast data printers which use the principles of electrophotography, charge images are generated on a charge image carrier such as a photoconductive drum and are subsequently inked with a black powder (toner) in a developing station. With the use of a photoconductive drum, the toner images are subsequently transferred onto normal paper and are fixed there. As a rule, a two-component developer is employed for developing, being composed of ferromagnetic carrier particles and of toner particles. The developer mix is normally conducted past the charge image carrier by means of a magnetic brush arrangement, the toner particles adhering to the charge image due to electrostatic forces. Such a developing station is shown, for example, in German AS 21 66 667.
Since the developer mix loses its tribo-electric properties with the passage of time, it must be replaced with a new developer mix at the end of its service life. The replacement of the developer mix must be capable of being carried out simply.
In U.S. Pat. No. 3,764,208 there is a disclosure of a device for removing developer mix from a developer station of an electrophotographic device. The device includes a developer roll and a mixing screw at the bottom of which there is a discharge opening comprising a pipe for the connection of a receptacle which accepts the developer mix from the floor of the developing station. To remove the developer mix, the rotational sense of the mixing screw of the developer drum is reversed in order to transport the developer mix into the discharge opening.
In such devices, there is the risk that the mix can unintentionally flow out in the region of the discharge pipe. There is also a risk of contaminating the surroundings when connecting and removing the receptacle. A complete emptying is not possible since the screw and the screw channel associated therewith must also have a defined distance from one another. The overall emptying process also lasts a relatively long time. As experience has shown, the toner may become caked and become lodged at the screws.